Wall construction



Oct. 25, 1955 N. NELSSQON ET AL 2,721,471

WALL CONSTRUCTION Filed July 25, 1951 23\ j@ @622 f a United States Patent O WALL CONSTRUCTION Nels Nelsson, Chicago, and George W. Baker, Chicago Heights, lil., assignors to United States Gypsum Company, Chicago, Iii., a corporation of Illinois Application July 26, 1951, Serial No. 238,702

2 Claims. (Cl. 72-16) This invention relates to a wall construction and more particularly to the problem of prevention of cracks being formed in the surface of a solid plastered partition.

Heretofore in walls of this type cracks in the plaster surface were likely to occur, as the wet plaster coat dried, at points on the surface where portions of rigid structural elements, such as door buck supports, conduits and the like, were exposed to the wet plaster. Various efforts have been made to rectify this situation by placing metal lath over the exposed portions of the rigid structural elements, but these efforts have been unsuccessful in reinforcing the plaster against the formation of cracks .001" to .008 wide.

The theory behind this crack formation is not clearly understood but it is believed to be due primarily to the relatively soft plasterboard surface shrinking a certain amount and the exposed portions of the rigid structural elements shrinking a diierent amount or not at all as the wet plaster coat applied thereto dries.

The drying shrinkage of a section through a partition consisting of plaster-plasterboard-plaster is greater than the drying shrinkage of a similar partition section consisting of plaster-rigid element-plaster. The imposition of a relative resilient member between the plaster and rigid member allows the latter section to shrink similarly to the plaster-plasterbcard-plaster section. f

Thus it is one of the objects of this invention to provide means for compensating for this shrinkage differential thereby causing the entire plaster receiving surface of the wall to shrink uniformly as thewet plaster applied thereto dries.

It is a further object of this invention to provide means which may be readily incorporated in a plastered wall by an unskilled workman so as to prevent the formation of cracks at places in the wall where rigid structural elements have portions thereof exposed to the plaster coat.

It is a further object of this invention to provide means for preventing the formation of cracks in a wall which is simple in construction, eifective in operation, and inexpensive to produce.

Further and additional objects will appear from the description, accompanying drawings, and appended claims.

In accordance with one embodiment of this invention, a wall construction is provided comprising a plaster receiving base member having wet plaster applied thereto, and a rigid structural element embedded in said member and having a lportion thereof exposed to the wet plaster. As the wet plaster dries, the surface of the base member on which the wet` plaster is applied shrinks a certain amount whereas the portion of the rigid element exposed to the wet plaster will shrink a dilerent amount or not at all. To compensate for the shrinkage differential between the base member and the structural element, resilient means is provided which engages the base member and assumes an enveloping relation with respect to the exposed portion of said structural element.

ice

For a more complete understanding of this invention reference should be made to the drawings, wherein Fig. l is a fragmentary elevational view of a solid plaster wall construction embodying one form of the invention as used in conjunction with an embedded electrical conduit, portions of the plaster being cut away to expose underlying parts;

Fig. 2 is a fragmentary sectional view taken along line 2 2 of Fig. l;

Fig. 3 is similar to Fig. 1 showing a modified form of the invention;

Fig. 4 is a fragmentary sectional view taken along line 4 4 of Fig. 3;

Fig. 5 is similar to Fig. 4 but showing another modied form of the invention; and

Fig. 6 is similar to Fig. 4 but showing still another modified form of the invention.

Referring now to the drawings, a solid plaster partition is shown comprising a plurality of coplanar plasterboard panels 10 arranged in abutting edge-to-edge relation. Each panel extends the full height of the partition and has the lower end thereof seated in a oor runner 11. The upper edge of each panel is secured by clips 12 or any other suitable means to a ceiling runner 13. Embedded in the plasterboard panels is a rigid structural element, which in this instance, is an electrical conduit 14' terminating at switch box 15. As seen in Figs. 1

and 3, the switch box 15 and conduit 14 are partially exposed to the plaster coats 18 which are subsequently applied to opposite sides of the plasterboard panels 10.

Each plasterboard panel 10 is of conventional constructionV and is formed of gypsum core 16 which is sandwiched between cardboard or paper sheets 17 as seen in Figs. 2 and 4.

The front face of the switch box 15 remains exposed in the finished wall and therefore does not present a serious crack-forming problem. The conduit 14, on the other hand, is completely hidden by the plaster coat 18. The conduit 14 is normally formed of metallic tubing having a relatively hard peripheral surface.

The theory behind the crack formations in the finished plastered surface is not clearly understood but it is'believed that the sheet 17 of panel 10, on which the wet plaster coat 18 is applied, initially expands upon the application of the wet plaster and then shrinks a certain amount during the drying of the plaster. The periphery of the rigid element, on the other hand, which is exposed to the coat remains relatively unaffected during the drying of the plaster. Therefore, the drying shrinkage of a section through the partition consisting of plaster-plasterboard-plaster is greater than the drying shrinkage of an adjacent section of the partition consisting of plaster-rigid element-plaster. The shrinkage differential between these adjacent partition sections causes stresses and strains in the plaster coat to develop which result in the formation of cracks.

One structure for overcoming this crack-forming diiculty and compensating for the shrinkage differential between the panel and conduit surfaces is shown in Figs. 1 and 2. This structure comprises a sleeve 20, formed of yieldable felt or layers of waterproof, or at least waterresistant, paper, which completely encloses or envelops the conduit 14. The sleeve 20 provides a yieldable medium between the wetA plaster coat and the relatively hard,vnonshrinkable periphery of the conduit 14. As the Wet plaster dries, the yieldablev sleeve 20 enables the movement of the plaster, covering over the conduit, to take place normal to the face of the partition entirely independent of the conduit.

Where the rigid structural element is of considerable expanse or width, an elongated piece of expanded metal or other foraminous material may be used in addition to sleeve 20 to reinforce the plaster similar to that shown in Fig. 6. The reinforcing `piece is of substantially the same length as the conduit and overlays the exposed portionof 1the sleeve 20. lhe elongated `edgesof the piece are benttafslightamount towardtheadjacent panel `prtions, and ;are secured thereto .by staples or any other suitable means 22T.

.A second .form of construction for preventing the formation of cracks adjacent conduit 14 is shown in Figs. 3 and 4. In this form, the sleeve 26 is replaced hy-,a yieldable backing orplasterbarrier 22, formed preferably of paper, fabric, or the like. The barrier 22 is substantially .the `same length .as the 4exposed portion of the conduit 14 and is disposed in spaced overlayingLrelation withzrespect tozthe conduit. Theelongated edges of the barrier are secured by staples 22 or any/other suitable means .to .theportionsv of .the panel, .or panels, disposed adjacent the conduit, The space 21 between the conduitlandthe .barrier 22, .enables the barrier 22 .to yield a suicient amount during :the drying of the plaster coat.18,.app1ied thereto, iso .as to prevent the formation ofgcracks .in the finished plastered surface. Where the barrier .22 is formed of a .compressible material a space 211is notrequired and the barrier 22 may .directly engage the4 periphery `of conduitll, as seen in the modified form in.=Fig. `5. In :such aninstance the barrier 22 itself will compress so `as `to lrelieve any stresses or strains which mightdevelop during the drying ofthe plaster. It will bewobserved in Fig. -4 that the barrier 22 is secured to only one side of the conduit 14, however there is no crack formationduring the drying of the plaster coating 18a, applied directly to Vthe exposed portion of conduit 14.

The unexpected result `obtained in this modified form of construction, particularly as to coating 18a, is not readily understood but itis believed to be due to the fact that-the edges 23.and 24, which are ,adjacent the conduit 14, are caused to move a slight amount toward coat 18a as'the surface of the panel exposed to the plaster coating 18a shrinks. This movement of the edges 23 and 24 is facilitated by the air pockets 25 and 26, respectively, formedron the opposite surface-.of the panel by barrier22. The :moving of the edges 23 and 24 is believed to cornpensate for the `shrinkage Adifferential between the panel andieonduit without causingstresses and strains to develop inthe plaster coating 18a. The edges 23 and 24 are in close proximity with respect to `the periphery of the conduit .and v.therefore the plaster coating V18a is prevented from Viindingits vway into the air pockets 25 and 26 when thecoating is being applied to the panel 10.

When. it is desired to reinforce the plaster adjacent the exposed ,portion of the conduit 14,.a reinforcing piece 27, similar to -that heretofore described, is employed which overlays the Vside of the `barrier 22 exposed to the plaster. The piecefmaybe formed of metal lath or any othersuitablezforaminousmaterial. To .facilitate mounting of the harrer-22 .andreinforcing ,piece 27, the former may be secured'alongits elongated .edges directly to the concave surface 'of the latter ,to form a unitary member 28. In Fig. one of said unitary members 28 has replacedthe single barrier v22 shown in Fig. 4. A unitary member 28 is` employed .on both vsides of the conduit 14, in the form of the construction invFig. 6..

Thusitwill be seen that simple inexpensive means have been provided which effectively prevent the formation of cracks in a solid lplaster partition vat points where rigid structural elements are embedded in the wall and have portions thereof exposed to aplaster coat subsequently applied thereto.

While several embodiments of this invention are shown above, it will be understood, of course, that the invention is not to be limited thereto, since many modifications may be made, and it is contemplated, therefore, by the appended claims, to cover any such modifications as fall within the true spirit and scope of this invention.

We claim:

l. A solid plaster wall construction comprising a plaster-receiving base member subjected to dimensional changes when a wet plaster coat is applied to opposite surfaces thereof 'and subsequently dried thereon, said base member being provided with an elongated opening, an elongated structural element substantially stable to dimensional changes due to the drying of a wet plaster coat applied thereto, said element being positioned within said base memberopening and having'elongated portions of the outer periphery thereof protruding outwardly from and beyond the opposite surfaces of said base member, an elongated-compressible shield disposed on at least one surface of .said `basemember and spanning said base member opening and beingrin contact with the adjacent outwardlyprotruding peripheral vportion of said element, said shield being substantially the same `length as the elongatedprotruding portions of said element and having marginal Iportions of said shield secured to the surface sections of said base member disposed in circumjacent relation with respect to said opening, and a plaster coat applied .to opposite surfaces of said base member and only the exposed surface of said shield whereby the latter effects separation of said plaster coat applied thereto and the protruding peripheral portion of said element in contact .with -said shield.

2. A solid plaster'wall construction comprising a plaster-receiving :base member subjected to dimensional changes when a wet plaster coat is applied to opposite surfaces `thereof and subsequently dried thereon, said base member being provided with an elongated opening, an elongated structural element substantially stable to dimensional changes due to the drying of a wet plaster coat appliedlthereto, saidelement being positioned within said base member opening and having elongated portions of the -outer periphery thereof protruding Loutwardly from and beyond the opposite surfaces of said base member, an elongated compressible shield disposed on at least one surface-of said base member and spanning said base memberopening and being in contact with the adjacent outwardly protruding 4peripheral portion of said element, said .shield .being substantially the same length as the elongated protruding portions of said element and having marginal portions kof said shield secured to the surface sections of said base member disposed in circumjacent relation kwith respect .to said opening, a foraminous plaster-bonding unit 'overlying the exposed surface of said shield and being o'f substantially the same dimensions as the latter, marginal portions of Vsaid unit likewise being secured .to the surface sections of said base member disposed Vin circumjacent relation with respect to said opening, and a plaster coat applied to opposite surfaces of said base member and only the exposed surface of said shield and the foraminous unit overlying the latter whereby said-s'hield effects separation'of said plaster coat applied thereto, and the protruding peripheral portion of said element in contact 'with 'said shield.

References Cited'in the le of this patent UNITED-"STATES PATENTS '1,596,623 Pomerantz Aug. 17, 1926 1,998,448 Crowe Apr. 23, 1935 2,078,049 Benedict Apr. 20, 1937 

